Recommended options for the Email Marketer tool

[marketingpro]

Hi! We are using the Email Marketer tool to send several automatic emails for new customers (after X days).

We've been using the "Product/Service Related" type for all those emails, because it was better to segment which customers get those emails. For example, we don't want to send all our lifecycle emails if they buy a small addon or service. Or if they only have a deactivated/cancelled product. We also don't want the same customer to receive the same email twice if they have 2 different products (specially if one is just an addon to the main one). 

The problem we've had is that we've been adding new products to WHMCS but didn't remember to activate the automatic emails (Email Marketer emails) for these new products. We don't want this to happen again, so we are thinking of possible solutions.

We've seen the "Client Related" type (opposed to our current  "Product/Service Related" type), and I guess with that option we don't have to worry about forgetting to activate the emails for new products. But we are not sure how that would work and if it will have other problems/risks. For example, it's not clear to me if a Client will still receive the automatic emails if they only have deactivated/cancelled products. 

Could you please recommend us the best solution for our needs or at least point us to relevant documentation about the Email Marketer tool? (especially about how the "Client Related" type works exactly)

Thanks!